c++ primer 学习笔记-第七章

习题7.1：

#include <iostream>
#include <string>

using std::cin; using std::cout;
using std::endl; using std::string;

struct Sales_data
{
string bookIsbn;
unsigned units_sold = 0;
double price = 0.0;
double revenue = 0.0;
};

int main(){
cout << "this is a test:" << endl;
Sales_data total;
if (cin >> total.bookIsbn >> total.units_sold >> total.price)
{
Sales_data trans;
while (cin >> trans.bookIsbn >> trans.units_sold >> trans.price)
{
if (total.bookIsbn == trans.bookIsbn)
{
total.revenue = total.price*total.units_sold + trans.price*trans.units_sold;
cout << total.revenue << endl;
total.units_sold += trans.units_sold;
total.price = total.revenue / total.units_sold;
}
else
{
cout << "书号：" << total.bookIsbn << " 已售本数："
<< total.units_sold << " 平均价格：" << total.price << endl;
total = trans;
}
}
cout << "书号：" << total.bookIsbn << " 已售本数："
<< total.units_sold << " 平均价格：" << total.price << endl;
}
else
{
cout << "你输入了个啥？大萨比！" << endl;
}
getchar();
getchar();
return 0;
}

习题7.2-7.3：

头文件Sales_data.h：

#ifndef SALES_DATA_H
#define SALES_DATA_H

#include <string>
using std::string;
//类
struct Sales_data
{
//成员函数
string isbn()const;
Sales_data &combine(const Sales_data &);
//成员变量
string bookIsbn;
unsigned units_sold = 0;
double revenue = 0.0;
};

#endif

Sales_data.cpp：

#include <string>
#include "Sales_data.h"

using std::string;

string Sales_data::isbn()const
{
return bookIsbn;
}
Sales_data & Sales_data::combine(const Sales_data &rhs)
{
units_sold += rhs.units_sold;
revenue += rhs.revenue;
return *this;
}

源.cpp：

#include <iostream>
#include <string>
#include "Sales_data.h"
using std::cin; using std::cout;
using std::endl; using std::string;

int main(){
cout << "this is a test:" << endl;
Sales_data total;
if (cin >> total.bookIsbn >> total.units_sold >> total.revenue)
{
Sales_data trans;
while (cin >> trans.bookIsbn >> trans.units_sold >> trans.revenue)
{
if (total.isbn() == trans.isbn())
total.combine(trans);
else
{
cout << "ISBN编号：" << total.isbn() << " 已售出："
<< total.units_sold << " 平均价格：" << total.revenue / total.units_sold
<< " 总收益：" << total.revenue << endl;
total = trans;
}
}
cout << "ISBN编号：" << total.isbn() << " 已售出："
<< total.units_sold << " 平均价格：" << total.revenue / total.units_sold
<< " 总收益：" << total.revenue << endl;
}
else
{
cout << "特么的啥也没有？" << endl;
}
getchar();
getchar();
return 0;
}

习题7.6：

非成员函数定义所在cpp：

#include <iostream>
#include <string>
#include <stdexcept>//使用runtime_error
#include "Sales_data.h"

using std::cin; using std::cout; using std::endl;
using std::string;
using std::runtime_error;
//成员函数
string Sales_data::isbn()const
{
return bookIsbn;
}
Sales_data & Sales_data::combine(const Sales_data &rhs)
{
units_sold += rhs.units_sold;
revenue += rhs.revenue;
return *this;
}

//非成员函数
istream & read(istream &is, Sales_data &item)
{
double price = 0;
is >> item.bookIsbn >> item.units_sold >> price;
item.revenue = item.units_sold*price;
return is;
}
ostream & print(ostream &os, const Sales_data &item)
{
os << "ISBN编号：" << item.isbn() << " 已售出："
<< item.units_sold << " 平均价格：" << item.revenue / item.units_sold
<< " 总收益：" << item.revenue;
return os;
}
Sales_data &add(const Sales_data &lhs, const Sales_data &rhs)
{
Sales_data sum = lhs;
while (true)
{
try{
if (lhs.isbn() == rhs.isbn)
{
sum.combine(rhs);
return sum;
}
else
throw runtime_error("输入的ISBN不相同,不能相加！");
}
catch (runtime_error err){
cout << err.what() << endl
<< "Oops, try again? Enter Y/N." << endl;
char c;
cin >> c;
if (!cin || tolower(c) == 'n')
break;
}
}
cout << "输入不正确，接下来的结果不予保证！" << endl;
return sum;//到这里应该只是随意返回一个错误对象了
}

习题7.7：

#include <iostream>
#include <string>
#include "Sales_data.h"
using std::cin; using std::cout;
using std::endl; using std::string;

int main(){
cout << "this is a test:" << endl;
Sales_data total;
if (read(cin,total))
{
Sales_data trans;
while (read(cin,trans))
{
if (total.isbn() == trans.isbn())
total.combine(trans);
else
{
print(cout, total) << endl;
total = trans;
}
}
print(cout, total) << endl;
}
else
{
cout << "特么的啥也没有？" << endl;
}
getchar();
getchar();
return 0;
}

习题7.9：

Person.cpp

#include <iostream>
#include "Person.h"

using std::cin; using std::cout; using std::endl;
using std::istream; using std::ostream;

istream &read(istream &is, Person &person)
{
is >> person.name >> person.address;
return is;
}
ostream &print(ostream &os, const Person &person)
{
os << "姓名：" << person.name << " 家庭住址：" << person.address;
return os;
}

习题7.11：

头文件：

#ifndef SALES_DATA_H
#define SALES_DATA_H

#include <string>
using std::string;
using std::istream;
using std::ostream;
//类
struct Sales_data
{
//成员函数
string isbn()const;
Sales_data &combine(const Sales_data &);
//构造函数
Sales_data() = default;
Sales_data(const string &s) :bookIsbn(s){};
Sales_data(const string &s, unsigned int n, double p) :bookIsbn(s), units_sold(n), revenue(p*n){};
Sales_data(istream &is);

//成员变量
string bookIsbn;
unsigned units_sold = 0;
double revenue = 0.0;
};

istream &read(istream &is, Sales_data &item);
ostream &print(ostream &os, const Sales_data &item);
Sales_data &add(const Sales_data &lhs, const Sales_data &rhs);

#endif

cpp文件：

#include <iostream>
#include <string>
#include <stdexcept>//使用runtime_error
#include "Sales_data.h"

using std::cin; using std::cout; using std::endl;
using std::string;
using std::runtime_error;

//类外定义的构造函数
Sales_data::Sales_data(istream &is)
{
cout << "请输入ISBN、已售数目、书本单价：" << endl;
read(is, *this);
}
//成员函数
string Sales_data::isbn()const
{
return bookIsbn;
}
Sales_data & Sales_data::combine(const Sales_data &rhs)
{
units_sold += rhs.units_sold;
revenue += rhs.revenue;
return *this;
}

//非成员函数
istream & read(istream &is, Sales_data &item)
{
double price = 0;
is >> item.bookIsbn >> item.units_sold >> price;
item.revenue = item.units_sold*price;
return is;
}
ostream & print(ostream &os, const Sales_data &item)
{
os << "ISBN编号：" << item.isbn() << " 已售出："
<< item.units_sold << " 平均价格：" << item.revenue / item.units_sold
<< " 总收益：" << item.revenue;
return os;
}
Sales_data &add(const Sales_data &lhs, const Sales_data &rhs)
{
Sales_data sum = lhs;
while (true)
{
try{
if (lhs.isbn() == rhs.isbn())
{
sum.combine(rhs);
return sum;
}
else
throw runtime_error("输入的ISBN不相同,不能相加！");
}
catch (runtime_error err){
cout << err.what() << endl
<< "Oops, try again? Enter Y/N." << endl;
char c;
cin >> c;
if (!cin || tolower(c) == 'n')
break;
}
}
cout << "输入不正确，接下来的结果不予保证！" << endl;
return sum;//到这里应该只是随意返回一个错误对象了
}

源文件：

#include <iostream>
#include <string>
#include "Sales_data.h"
using std::cin; using std::cout;
using std::endl; using std::string;

int main(){
cout << "this is a test:" << endl;
/*
Sales_data total;
if (read(cin,total))
{
Sales_data trans;
while (read(cin,trans))
{
if (total.isbn() == trans.isbn())
total.combine(trans);
else
{
print(cout, total) << endl;
total = trans;
}
}
print(cout, total) << endl;
}
else
{
cout << "特么的啥也没有？" << endl;
}
*/
Sales_data book1, book2("Harry Potter"), book3("C++ primer 5th", 10, 110), book4(cin);
print(cout, book1) << endl;
print(cout, book2) << endl;
print(cout, book3) << endl;
print(cout, book4) << endl;
system(0);
getchar();
getchar();
return 0;
}

习题7.13：

#include <iostream>
#include <string>
#include "Sales_data.h"
using std::cin; using std::cout;
using std::endl; using std::string;

int main(){
cout << "this is a test:" << endl;

Sales_data total(cin);
if (!total.isbn().empty())
{
while (cin)//到最后一条时 此处不是输入数据的地方，cin返回true
{
Sales_data trans(cin);//调用read()，但是ctrl^z，不输入，默认初始化,继续向下走
if (total.isbn() == trans.isbn())//可在else下加入cout测得trans.bookIsbn为空，返回0，进入else
total.combine(trans);
else
{
print(cout, total) << endl;//这样写可以保证最后一条数据正常显示
total = trans;
}
}
}
else
{
cout << "特么的啥也没有？" << endl;
}

getchar();
getchar();
return 0;
}

习题7.15：

Person.h：

#ifndef PERSON_H
#define PERSON_H

#include <iostream>
#include <string>

using std::string;
using std::cin; using std::cout; using std::endl;
using std::istream; using std::ostream;

struct Person;
istream &read(istream &is, Person &person);//istream版构造函数需要使用read，此处为前置声明
struct Person{
//构造函数
Person() = default;
Person(const string &n, const string &addr) :name(n), address(addr){
//cout << "请输入您的姓名、家庭住址：" << endl;
}
Person::Person(istream &is){ read(cin, *this); }
//成员变量
string name = "毛蛋";
string address = "合群新村";
//成员函数
auto getName()const->const string & { return name; }//返回对象姓名
auto getAddress()const->const string & { return address; }//返回对象家庭住址
};
//非成员对象
istream &read(istream &is, Person &person);//读入Person对象信息
ostream &print(ostream &os, const Person &person);//打印Person对象信息
#endif

习题7.23：

Screen.h：

#ifndef SCREEN_H
#define SCREEN_H

#include <iostream>
#include <string>
#include <vector>
#include <iterator>

using std::cin; using std::cout; using std::endl;
using std::string; using std::vector;

class Screen{
public:
using pos = string::size_type;//类型别名
//构造函数
Screen() = default;
Screen(pos ht, pos wd, char c) :height(ht), width(wd), contents(ht*wd, c){}
//成员函数
char get()const{ return contents[cursor]; }
char get(pos r, pos c)const{ return contents[r*width + c]; }
Screen &move(pos r, pos c);
private:
//成员变量
pos cursor = 0;
pos height = 0, width = 0;
string contents;
};
#endif

Screen.cpp：

#include <iostream>
#include <string>
#include <vector>
#include <iterator>

#include "Screen.h"

using std::cin; using std::cout; using std::endl;
using std::string; using std::vector;

inline Screen & Screen::move(pos r, pos c)
{
cursor = r*width + c;
return *this;
}

习题7.24：

#ifndef SCREEN_H
#define SCREEN_H

#include <iostream>
#include <string>
#include <vector>
#include <iterator>

using std::cin; using std::cout; using std::endl;
using std::string; using std::vector;

class Screen{
public:
using pos = string::size_type;//类型别名
//构造函数
Screen() = default;//1
Screen(pos ht, pos wd) :height(ht), width(wd), contents(ht*wd, ' '){}//2
Screen(pos ht, pos wd, char c) :height(ht), width(wd), contents(ht*wd, c){}//3
//成员函数
char get()const{ return contents[cursor]; }
char get(pos r, pos c)const{ return contents[r*width + c]; }
Screen &move(pos r, pos c);
private:
//成员变量
pos cursor = 0;
pos height = 0, width = 0;
string contents;
};
#endif

习题7.42：

#ifndef BOOK_H
#define BOOK_H

#include <iostream>
#include <string>
using std::string;
using std::istream;
class Book
{
friend void read(istream &is, Book book);
public:
Book(const string &a, const string &n, const string &i, const string &d)
:author(a), name(n), isbn(i), pubdate(d)
{ }
Book() :Book("", "", "", ""){}
Book(const string &book_name) :Book(book_name, "", "", ""){}
Book(istream &is) :Book(){ read(is, *this); }
private:
string name;
string isbn;
string author;
string pubdate;
};

void read(istream &is, Book book)
{
std::cout << "请输入书名、ISBN、作者、出版日期" << std::endl;
is >> book.name >> book.isbn >> book.author >> book.pubdate;
}

#endif

习题7.42：